diy solar

diy solar

Small FM transmitter hooked to solar panel for constant power and to charge battery

jonnyvee

New Member
Joined
Jan 16, 2021
Messages
8
I am trying to figure out the best battery and solar panel to use with a small transmitter I have to pick up the animal sounds in the back yard (Birds,etc) This is what I have as far as specs
  • Output Power: 100 mW
  • Equivalent Noise: >= 30 dB
  • Power Supply Voltage: DC 3.0 V - 5.0 V
  • Operating Current: 35 mA
  • Sound Track: LINE/USB channel (stereo); MIC channel (single channel)
I have hooked it to 3 AA batteries that are 2000 mAh each and it will run for about 34 hours and then die as the voltage goes below 3 volts, I would like to hook it to a battery or two that I can attach a small solar panel to and keep them charged all the time so I'm not having to put in new batteries every day or two.
I have been reading and the more I do the more confused I get.

I was thinking of and let me know if this sounds right, a 3.5 - 5 volt battery pack at around a 3000 mAh or maybe 2 wired together to last longer and a 6 volt, 1 watt at 500 or so mAh panel for charging along with a small charge controller, I'm in Michigan so the sun is a issue some times
I have almost zero experience with this stuff and would like to keep this as small as possible
 
Thanks for the info but way to large all the way around, I'm thinking smaller something I can hang off a branch, with the 3 batteries I start out with about 3.6 volts and after 34 hours it goes to about 2.6 volts and shuts down so basically I loose 1 volt and some amp hours but I have no idea what that means, I get more confused the more I read, if I run at somewhere between 4-5 volts with a stronger battery (more mAh) wouldn't a 6volt panel charging at 1 Watt and 500 mAh with a controller of some kind work to keep it charged every day as it wouldn't go completely dead but just kind of need topped off every day or am I completely in the wrong ballpark?
Something like a 18650 battery which is 3.7 volts and 5000 mAh
 
Battery chemistry determines the starting voltage, not its "strength".

18650 Li-ion battery is actually 4.2V peak, but most only have a legitimate capacity of 4Ah, so you're not much further along. Without proper voltage regulation, a 6W panel would destroy the cells.

A more sensible solution might be a Lithium iron phosphate:


Get a cell holder and put 2-4 of them in parallel.

2.5W panel:

And a suitable 5V to 3.3V converter.
 
Starting to understand it a bit more, it says max charging is 1.5watts so I could get away with a panel that puts out 1.5 watts and a converter then right? trying to be around 4 inch panel if possible
 
What says max charging 1.5W?

We've established that you need 9Wh of energy in a 34 hour period. Unlikely that a 1.5W panel can consistently keep the system charged, particularly if solar availability OR shading is a concern (even a little shading can almost disable panel output).

A HIGHLY efficient 4" panel will output a maximum of 2W, and that may not get you what you need.
 
I Misunderstood, the link you sent for the battery says 1.5amps max not watts, I'll get a few of those batteries and find the smallest 2.5 watt panel I can that has a good rating and go from there
Thanks again for the info, hopefully this works out
 
Ah... 1.5A * 3.2V = 4.8W, and that's PER CELL, so if you have 4 cells, almost 20W.
 
Can I use one of those small Buck Converters on this? From what they say it should work
 
Yes. 2.5W panels to a buck converter provided it's compatible with the output voltage of the panel. I'm not sure if the prior one I linked will work, but it might.
 
Possibly. Would need an enclosure if outdoors. Not sure what the unit would do in the event of a low-input voltage/current, i.e., cloudy day, panel underperforming, etc. I don't see low voltage protection, but it has other protections. Set output to 3.3V to ensure it's below the panel output of 5V.
 
So I have a 3.5 watt 6volt panel that does 600Ma and this buck converter D-PLANET [4-PACK] 5A DC-DC Adjustable Buck Converter 4~38v to 1.25-36v Step Down Power Supply High Efficiency Voltage Regulator Module I also have a 18650 3.7 Lithium Ion battery that is 2200Ma, I have the buck converter putting out 4.2volts as that's full charge on the battery but do I need a converter/charger that shuts off power to the battery when it reached full charge? been reading these batteries don't like to be overcharged, I don't know if keeping that voltage going to it will damage the battery or not and still a bit confused on this stuff
 
Back
Top